A battery module includes a cell stack structure formed as a plurality of battery cells stacked and accommodated in a module case. The module case includes at least one hole forming plate having a plurality of resin injection holes formed therein for receiving an adhesive resin therethrough, and the plurality of resin injection holes are distributed on both a left side and a right side of a center of the hole forming plate in a longitudinal direction thereof, such that the resin injection holes on the left side and the right side are spaced apart from each other by a predetermined distance from the center of the hole forming plate in the longitudinal dimension.